This invention relates to novel branched starch and starch hydrolyzates, solutions thereof, and methods of making and using them.
The molecular structure and origins of starch are well documented in the literature. Starch from plant sources typically exists in two forms, amylose and amylopectin. Amylose is a linear polymer of glucose linked by alpha 1-4 glycosidic bonds. Amylopectin is a branched polymer of glucose containing up to 4% alpha 1-6 glycosidic bonds and about 96% alpha 1-4 glycosidic bonds. It is the 1-6 bonds which create the branches in an otherwise linear polymer. Starch normally is found in nature as a mixture of about 25% amylose and 75% amylopectin. So called waxy varieties of plants exist which contain up to 100% amylopectin. Corn processed by the corn processing industry is, for the most part, dent corn, although small amounts of waxy or a high amylose variety are also processed into specialty products.
Amylose molecules or partial hydrolyzates thereof, because they are linear tend to associate through hydrogen bonding with themselves and with other amylose molecules to form essentially water-insoluble aggregates. The process of insolubilization is usually termed retrogradation. This phenomenon is problematic in the starch processing industry in that it causes processing difficulties in the production of carbohydrate products from starch. Perhaps more importantly, retrogradation phenomena cause defects in product quality, such as hazing, precipitation and clouding in solutions of the carbohydrates. Stable solutions of carbohydrates are deemed desirable in the industry.
As such, there is a need for new carbohydrates that form stable aqueous solutions as well as a need for a method of treating linear carbohydrates so as to overcome the retrogradation problems associated therewith. The present invention provides such carbohydrates and methods. These and other advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.
The present invention provides a starch that includes at least one glucose polymer having greater than 4% alpha 1-6 glycosidic linkages. The present invention further provides a starch hydrolyzate that includes at least one glucose-oligomer having greater than 4% alpha 1-6 glycosidic linkages. The starch and starch hydrolyzate of the present invention provide stable aqueous solutions that would not be attainable with unbranched linear poly- or oligo-saccharides. In this regard, the present invention provides a stable aqueous starch solution that includes one or more amylose molecules that are branched by one or more alpha 1-6 glycosidic linkages. The present invention also provides a stable aqueous starch hydrolyzate solution that includes one or more amylose hydrolyzate molecules that are branched by one or more alpha 1-6 glycosidic linkages.
The present invention further provides a method of improving the aqueous solution stability of a starch that contains amylose molecules, which method includes introducing one or more alpha 1-6 glycosidic linkages so as to branch one or more of the amylose molecules in the starch. The method of the present invention also can be applied to starch hydrolyzates, preferably those that contain amylose hydrolyzates. In this regard, the present invention provides a method of improving the aqueous solution stability of a starch hydrolyzate, which method includes introducing one or more alpha 1-6 glycosidic linkages so as to branch one or more of the amylose hydrolyzate molecules in the starch hydrolyzate.
The method of the present invention similarly applies to amylose and amylose hydrolyzates. In this respect, the present invention provides a method of improving the aqueous solution stability of amylose by introducing one or more alpha 1-6 glycosidic linkages so as to branch one or more of the amylose molecules. The present invention also provides a method of improving the aqueous solution stability of an amylose hydrolyzate by introducing one or more alpha 1-6 glycosidic linkages so as to branch one or more amylose hydrolyzate molecules.